linux-kernel - Re: [PATCH] PM / runtime: Fixup reference counting of device link suppliers at probe

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Message-ID: <1602619.cydcNSDU3f@aspire.rjw.lan>
Date:   Tue, 29 May 2018 10:59:45 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Ulf Hansson <ulf.hansson@...aro.org>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] PM / runtime: Fixup reference counting of device link suppliers at probe

On Friday, May 18, 2018 11:07:02 AM CEST Ulf Hansson wrote:
> On 18 May 2018 at 10:58, Rafael J. Wysocki <rafael@...nel.org> wrote:
> > On Fri, May 18, 2018 at 10:48 AM, Ulf Hansson <ulf.hansson@...aro.org> wrote:
> >> In the driver core, before it invokes really_probe() it runtime resumes the
> >> suppliers for the device via calling pm_runtime_get_suppliers(), which also
> >> increases the runtime PM usage count for each of the available supplier.
> >>
> >> This makes sense, as to be able to allow the consumer device to be probed
> >> by its driver. However, if the driver decides to add a new supplier link
> >> during ->probe(), hence updating the list of suppliers,
> >
> > Do any of the existing drivers do that?
> 
> Yes.
> 
> At least these, but possibly even more...
> 
> drivers/gpu/drm/rockchip/rockchip_drm_drv.c
> drivers/gpu/drm/tegra/dc.c
> drivers/gpu/ipu-v3/ipu-prg.c
> drivers/pci/dwc/pci-dra7xx.c
> 
> >
> >> the following call to pm_runtime_put_suppliers(), invoked after really_probe()
> >> in the driver core, we get into trouble.

Patch applied, thanks!